I have used an old clipboard that I sawed to fit, and sanded down the edges. Very sturdy and not very heavy.

Gee thanks so much; will try both methods.

I get left over sign material. Some of it is solid plastic, some have 'channels'. Go to your local sign shop and ask if they have any scraps, usually inexpensive, sometimes free!!!

I use the heavyweight template plastic. And I have seen where people have used the needlepoint plastic. But I have a lot of the HW template (found huge pkg of clearance a year or so ago), so I use that. AND it goes through the washing machine like a breeze.

I use $1.00 placemats for the bottoms of mine. Easy to cut and can't get much cheaper. I just make a sleeve and slide it in.

I use very, very thin (less than 1/8") masonite that my hubby cuts to size for me. Put it in a sleeve that matches the lining. Doesn't add any weight that I have noticed to the finished bag. Bonus is after he's cut 4 bottoms, there is still have enough left that I can make lots more bags!

I think the foam core you used sounds good.

I've used Matte board --

I use the same thing and it works great. I found it in Home Depot/Lowes - they sold it in the same area where you get new keys made up.

Good luck!

I also use this in the bottoms. Plastic canvas is just too flimsy and nothing else seemed to hold up. Not had a problem and very sturdy and cheap enough too.